This invention relates to an odorless or low-odor crosslinkable compound and an odorless or low-odor resin composition containing the same. More particularly, this invention relates to an odorless or low-odor crosslinkable compound obtained by reacting an aromatic hydrocarbon-formaldehyde resin with an .alpha.,.beta.-unsaturated monocarboxylic acid or its ester and an odorless or low-odor resin composition containing the crosslinkable compound.
Aromatic hydrocarbon-formaldehyde resins have been studied, for example, by A. J. Baeyer in the latter half of the 19th century and resinous products have been obtained by reacting an aromatic hydrocarbon such as benzene, toluene, xylene, mesitylene, durene, naphthalene, acenaphthene, or the like with formaldehyde in the presence of a strong acid catalyst (A. J. Baeyer; Ber., vol. 5, p. 1098 (1872), ibid., vol. 6, p. 223 (1873) and ibid., vol. 7, p. 1190 (1874)). Further, new knowledge as to condensation reaction of an aromatic hydrocarbon and formaldehyde was found by R. Wegler during the Second World War and the foundation thereof has been established (R. Wegler; Angew. Chem. A/60, No. 4, p. 88 (1948)).
In Japan, M. Imoto, K. Fu, and others have widely studied aromatic hydrocarbon-formaldehyde resins after the Second World War and given foundation of development, so that aromatic hydrocarbon-formaldehyde resins such as xylene-formaldehyde resin, and the like are manufactured industrially.
As is well known in the art, aromatic hydrocarbon-formaldehyde resins are generally viscous liquid and excellent in adhesive properties, water resistance, humidity resistance, acid resistance, alkali resistance, and electrical insulating properties. But when electrical insulating materials are obtained by condensation reaction with phenols, amines, or the like at high temperatures in the presence of an acid catalyst by applying reactivity of the methylol group, ether linkage and acetal linkage in the resin, there are many disadvantages in that water is by-produced by the condensation reaction, high temperatures are necessary for completing the reaction, and the like. In addition, low-molecular weight polymers such as prepolymers usually have an odor. When they are cured, a more offensive odor is emitted, which is not preferable from the viewpoint of health of the workers and residents therearound. Such a problem should also be solved.
On the other hand, since unsaturated polyester varnishes are relatively balanced in mechanical and electrical properties, heat resistance, workability, and production cost, they have been used in large amounts in glass fiber reinforced plastics, paints and varnishes, adhesives, electrical parts, and the like. Unsaturated polyester varnishes comprise mainly unsaturated polyester resin and a crosslinkable monomer which is usually contained in an amount of 40 to 60% by weight. As the crosslinkable monomer, a relatively low-molecular weight compound such as styrene has been used from the viewpoint of properties or economy. But since the compound has a low molecular weight and is very volatile, there are many disadvantages in that the weight of the varnish is lost in an amount of 20 to 60% by weight by vaporization in the state of varnish and at the time of curing, an irritating odor is emitted and is not preferable from the viewpoint of health of the workers and residents therearound, and the like.